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Why Do My Eyes Get Blurry at Night? 8 Common Causes & Solutions
Blurry vision at night (especially while driving) is a common concern for many of us and can occur for several reasons. In low light, your pupil widens, different retina cells adapt, and your eyes may be more fatigued after a day of digital device use. There are 8 common causes for blurry vision at night, including uncorrected refractive error, dry eye, cataracts, and normal age-related changes. Most causes can be managed with proper diagnosis and treatment. In this guide, we’ll explain why your vision can be blurrier at night, how it can be treated, and when it’s important to seek medical attention for your blurry vision.
How Your Eyes Function Differently at Night
Our eyes work differently at night compared to during the day. Iris size changes with different lighting conditions, and we used different retinal cells in the dark. The change in pupil size from 2-3 mm in light conditions to 7-8mm in dark conditions allows more peripheral light rays to enter the retina, which can magnify optical imperfections. In low light, different retinal cells are used as your eyes shift from photopic (bright-light, cone-dominant) to scotopic (low-light, rod-dominant) vision, which changes optical clarity.
Why Pupils Dilate, and Vision Gets Less Sharp
Your pupils dilate (mydriasis) in low light to allow more light into the eye so you can see better. Though the brightness increases, the clarity decreases. More peripheral light rays enter the eye when the pupil is larger, increasing optical imperfections and light scatter within the eye. This change can magnify small refractive errors, including astigmatism, and make glare or halos more noticeable. Furthermore, as the pupil enlarges, your depth of focus decreases, making some refractive errors more apparent, and vision appears less crisp at night.
Rod Cells and Low-Light Vision Adaptation
Rod cells are one of two types of specialized photoreceptors in the retina, and they provide vision in low-light conditions. Cone cells detect color and fine detail in bright light, whereas rods are sensitive to small amounts of light but do not perceive color. Your vision at night may appear more gray and less crisp. When lighting levels decrease, the visual system shifts from cone-dominant to rod-dominant function, which is called dark adaptation. Dark adaptation is the process by which rhodopsin, a light-sensitive pigment within rod cells, regenerates and sensitivity gradually improves over 20–30 minutes. Although rods enhance light detection, they provide lower resolution and contrast than cone cells, which is why visual clarity is reduced at night.
The 8 Most Common Causes of Blurry Night Vision
There are 8 common causes of blurry night vision. Uncorrected refractive error is the most common cause in all age groups, while the other causes may be more or less common depending upon patient demographics, age, and systemic/ocular health conditions.
Cause 1: Uncorrected Refractive Errors
Uncorrected refractive error is the most common cause of night vision blur and one of the leading causes of blurry vision in general.
. Nearsightedness (myopia), farsightedness (hyperopia), and astigmatism can become more noticeable in low light, when pupils dilate, allowing more peripheral light into the eye and increasing optical blur. Small prescription changes that may be insignificant during the day can significantly impact clarity while driving at night. Glare, halos, and difficulty reading street signs or seeing the lane lines on the road are common symptoms. Updating your glasses or contact lens prescription may be an effective treatment for night vision blurriness.
Cause 2: Dry Eyes
Dry eye is a common cause of blurry night vision because the tear film must be stable and clear for optimal visual acuity. The tear film is a refractive surface in front of the cornea. If it becomes uneven or evaporates too quickly, light will scatter instead of being focused sharply on the retina. Pupils dilate at night, which increases surface irregularities and glare, halos, and blur become more noticeable. Symptoms are often worse in the evening after prolonged screen or digital device use throughout the day. Environmental conditions, including increased exposure to heat/air/wind, can also exacerbate dry eye. Tear film stability can be improved with the use of artificial tears, more frequent blinking, or targeted dry eye treatments, as recommended by an eye doctor.
Cause 3: Age-Related Changes
Age-related changes after age 40, called presbyopia, can result in blurred vision at night (and during the day). As we age, the eye’s natural lens becomes less flexible, which reduces its ability to focus quickly and at a near distance. In dim lighting or at night, pupils dilate, and the depth of focus decreases, making small refractive errors more noticeable. Lenses become more yellowed with age, which can also scatter more light, reduce contrast, and increase glare from headlights or streetlights. Lastly, if you aren’t wearing the correct prescription glasses for reading, your eyes may have to work harder during the day than they should, which can result in blurry vision at night.
Cause 4: Digital Eye Strain
Digital eye strain from device use during the day can also result in blurrier vision at night. Prolonged screen use can overwork your focusing system and reduce your blink rate. Hours of near work can cause temporary accommodative fatigue in the ciliary body, making it harder for your eyes to shift focus clearly at different distances. In addition, we blink less than we should when using digital devices, leading to tear film instability, dry eye disease, and increased light scatter. Accommodative fatigue and ocular surface dryness can amplify glare, halos, and visual fluctuation when driving at night.
Cause 5: Cataracts
A cataract is the clouding and yellowing of a normally clear lens, which scatters light instead of focusing it on the retina. Pupils dilate in low-lighting or at night, which allows more light rays to pass through the cloudy lens, resulting in glare, halos, and starbursts around car lights and streetlights. Cataracts can also reduce contrast sensitivity, making it harder to distinguish objects in dark environments. Many patients note that night driving becomes extremely difficult. Cataracts need to be removed when they interfere with your acuity and glare, and surgery can restore clear, sharper vision.
Cause 6: Glaucoma
Glaucoma is a disease process that results in gradual damage to the optic nerve and peripheral (side) vision loss if left untreated. In the dark, contrast is reduced, pupils are dilated, and peripheral vision loss may be more noticeable while navigating or driving at night. Patients do not notice vision loss in the early disease process but may describe hazy, blurry, or areas of dimmed vision with more advanced disease. Annual eye exams for adults are important for early diagnosis, treatment to prevent further loss, and preservation of the remaining vision.
Cause 7: Diabetic Retinopathy
Diabetic retinopathy can cause blurry vision at night and during the day. Elevated blood sugar levels can damage the small blood vessels in the retina, resulting in leakage, swelling (macular edema), and/or a reduction in the eye’s oxygen supply. These changes reduce the retina’s ability to process light in low-light conditions. Fluctuating blood sugar levels can also cause swelling of the eye’s lens and temporary changes in visual clarity after eating. As the disease progresses, new, leaky blood vessels, a process called neovascularization, can form, which require laser treatment. The laser treatment results in peripheral retinal scarring and peripheral vision loss, which is more noticeable at night. Patients with diabetes need annual, dilated eye exams for early detection, treatment, and management.
Cause 8: Vitamin A Deficiency
Night blindness (nyctalopia) can be caused by a deficiency in vitamin A; however, it is rare in the United States for those on a proper diet. Vitamin A is needed to produce rhodopsin, a light-sensitive pigment in the rod cells of the retina that provides vision in low-light conditions. When vitamin levels are low, the rods do not function efficiently, leading to poor dark adaptation and problems seeing in the dark. Vitamin A deficiency can be reversible with proper medical evaluation and supplementation if diagnosed early. It is rare in those who live in the United States, with a normal diet affecting less than 1% of people, with a 2013 estimate at 0.3%.
When Dry Eyes and Digital Strain Affect Night Vision
Digital eye strain and associated dry eye can cause one’s vision to be blurrier at night. Tear production follows the circadian rhythm and declines later in the day. Prolonged screen use can also reduce tear film stability. Research shows that digital device users have a reduced blink rate of 54-61%, which results in tear evaporation and increased surface irregularities that scatter light. Indoor environmental factors like air conditioning, heating, ceiling fans, and low humidity can worsen evaporation. Wind, extreme temperatures, low humidity, air pollution, and allergens can also exacerbate dry eye disease.
The Digital Sunset Effect and Your Eyes
The digital sunset effect describes the visual discomfort and blur that can occur when your eyes must transition abruptly from prolonged bright screen exposure to dim evening lighting. Due to a combination of reduced tear production and eye fatigue after screen time, it can be difficult for your visual system to transition from focusing on a brightly lit device to a darker environment, such as night driving.
Immediate Solutions You Can Try Tonight
Blurry night vision that results from dry eye and digital strain can be improved with the use of preservative-free artificial tears, used proactively. Tears should be used in the morning and evening, and before extended screen time. Overhead lighting should be aimed away from screens to reduce glare. Some doctors will recommend the 20-20-20 rule: every 20 minutes, look 20 feet away for 20 seconds to relax focusing muscles and encourage blinking; however, the research is inconclusive whether this makes a difference.
Position your screens 20–24 inches from your eyes and slightly below eye level to reduce ocular surface exposure and tear film evaporation. Aim all air/heat vents away from you in the car, and wear sunglasses to protect your eyes from environmental exposure. Avoid using overhead fans at night. By changing lifestyle habits, many will notice improvement in their symptoms within 2–4 weeks.
When to See an Eye Doctor for Blurry Night Vision
Seek eye care immediately if you experience sudden vision loss, severe eye pain, flashes of light, a curtain-like shadow, or symptoms affecting only one eye. These can be symptoms of an urgent eye condition, such as a retinal detachment or acute glaucoma. Gradual blur, glare, or mild dryness should be addressed with a comprehensive eye exam, which includes visual acuity testing, refraction, tonometry, slit-lamp evaluation, and a dilated fundus exam. Most adults should have exams every 1–2 years.
Conclusion
Most night vision problems can be easily treated or managed. Schedule an eye exam for quick diagnosis and proper treatment. You should always see an eye doctor if your blurry vision is new to ensure it is not a serious condition. Dry eyes and uncorrected refractive errors are the most common causes, and when treated, can improve quickly. Cataracts and other systemic diseases may require a more managed approach, and the resolution depends on the condition and severity. If you experience sudden vision loss, flashes of light, a curtain-like shadow, or eye pain, you should see a doctor immediately.
FAQs on Why Eyes Get Blurry at Night
Mild blurry night vision can be common with aging. With age, the lens of the eye becomes less flexible, loses the ability to focus, and may develop early cataract changes. These changes may reduce contrast and increase glare. Significant or worsening night vision problems should always be evaluated, as they may be the result of a more serious condition. However, most causes are treatable with proper diagnosis and care.
Possibly, tear production does change throughout the day. Prolonged screen use can destabilize the tear film and exacerbate dry eye symptoms. In low light, dilated pupils can increase surface irregularities, so dry eye-induced blur, glare, and fluctuating vision may become more noticeable.
